# Instructor Guide for Week 6

We consider linear systems as state machines where the state is a vector of reals. Difference equations and differential equations are shown to describe such state machines. The notions of linearity and superposition are introduced, and convolution is touched upon (to be dealt with in more detail later).

This week is a good time for the first midterm, with coverage including chapters 1-4, and appendix A of the reader, except sections 4.7 and 4.8 (i.e., leaving out feedback, since until this week, they haven't worked any problems involving feedback).

### Problem session

- Review for midterm.